Line selector for pneumatic systems

ABSTRACT

A line selector for pneumatic tube systems. The line selector is provided for use in pneumatic tube systems of the type used to transport carriers from station to station. The line selector comprises a main housing having an inlet through which the carrier enters the main housing. The carrier selectively leaves the main housing either through a main outlet or a pair of branch outlets. A flexible coupling is located within the housing and attached at a first of its ends to the inlet and a seal assembly is coupled to the other end of the flexible coupling for receiving the carrier from the flexible coupling. The seal assembly and outlets define means for locating the seal assembly selectively against each one of the outlets and further includes means for pneumatically sealing the seal assembly to the selected outlet. A switching mechanism is operably attached to the main housing to move the seal assembly out of engagement with one of said outlets and into engagement with another of the outlets.

Weaver 1 Feb. 25, 1975 LINE SELECTOR FOR PNEUMATIC SYSTEMS [76] Inventor: Peter Brinkerhoff Weaver, 5

Brushwood Ct., Don Mills, Ontario, Canada [22] Filed: Jan. 30, 1973 [21] Appl. No.: 328,111

[30] Foreign Application Priority Data Feb. 2, 1972 Canada 133737 [52] US. Cl 243/31, 285/223, 285/417 [51] Int. Cl. B65g 51/18, B65g 51/24 [58] Field of Search 243/19, 29-31, 243/38; 285/223, 417

{56] References Cited UNITED STATES PATENTS 406,447 7/1889 Kennedy 243/31 944,680 12/1909 Litchfield 243/23 3,367,603 2/1968 Feyerherd 243/29 3,701,496 10/1972 Ekama 243/29 FOREIGN PATENTS OR APPLICATIONS 499,297 1/1939 England 243/29 20,468 9/1911 England..... 243/29 7,143 12/1908 England 243/29 1 Hi l .111111 3/1968 Germany 243/31 8/1964 France 302/2 R Primary Examiner-Richard A. Schacher Assistant Examiner--W. Scott Carson [57] ABSTRACT A line selector for pneumatic tube systems. The line selector is provided for use in pneumatic tube systems of the type used to transport carriers from station to station. The line selector comprises a main housing having an inlet through which the carrier enters the main housing. The carrier selectively leaves the main housing either through a main outlet or a pair of branch outlets. A flexible coupling is located within the housing and attached at a first of its ends to the inlet and a seal assembly is coupled to the other end of the flexible coupling for receiving the carrier from the flexible coupling. The seal assembly and outlets define means for locating the seal assembly selectively against each one of the outlets and further includes means for pneumatically sealing the seal assembly to the selected outlet. A switching mechanism is operably attached to the main housing to move the seal assembly out of engagement with one of said outlets and into engagement with another of the outlets.

18 Claims, 8 Drawing Figures PATENIED Fiazsms SHEET 1 ll? 5 SHEET 3 BF 5 1 LINE SELECTOR FOR PNEUMATIC SYSTEMS This invention relates to a line selector for pneumatic tube systems and in particular a line selector capable of receiving a carrier through an inlet and directing the carrier out through a main outlet or through one of two branch outlets as desired.

Pneumatic systems are used for transporting various items in carriers around buildings such as hospitals, high rise office complexes and the like. In most instances the pneumatic system is partially evacuated at one or more outlets so that air is inspired through inlets in the system and drawn from the inlets to the outlets. However, pressurized systems are also used. By arranging for a suitable movement of air between stations, it is possible to use the moving air to transport carriers between stations. In order that a carrier placed in the system at one station can find its way to a selected one of a plurality of other stations, it is necessary to provide the system with line selectors which can direct the carrier along one of several paths according to commands fed into the system by a control circuit.

It is an object of the present invention to provide a line selector for use in pneumatic systems, the line selector being relatively compact, inexpensive and reliable.

According to a preferred embodiment of the present invention, a line selector is provided for use in pneumatic tube systems of the type used to transport carriers from station to station. The line selector comprises a main housing having an inlet through which the carrier enters the main housing. The carrier selectively leaves the main housing either through a main outlet or a pair of branch outlets. A flexible coupling is located within the housing and attached at a first of its ends to the inlet, and a seal assembly is coupled to the other end of the flexible coupling for receiving the carrier from the flexible coupling. The seal assembly and outlets define means for locating the seal assembly selectively against each one of the outlets and further include means for pneumatically sealing the seal assembly to the selected outlet. A switching mechanism is operably attached to the main housing to move the seal assembly out of engagement with'one of said outlets and into engagement with another of the outlets.

The invention will be better understood with reference to the drawings, in which:

FIG. 1 is a top view of a line selector according to the invention;

FIG. 2 is a side view of the line selector;

FIG. 3 is an exploded perspective view of a flexible coupling used in the line selector;

FIG. 4 is a sectioned partial top view of the line selector showing the flexible coupling and other parts;

FIG. 5 is a sectional view on line 5-5 of FIG. 1 with the background removed for clarity;

FIG. 6 is a perspective, exploded view of part of the line selector, and more particularly of parts of switching mechanisms;

FIG. 7 is a diagrammatic view of a simplified pneumatic circuit incorporating the line selector; and

FIG. 8 is a view of part of an alternative embodiment of the line selector.

Reference is first made to FIGS. 1 and 2 to describe the general layout of a line selector constructed according to the invention. The selector is adapted to be connected into a pneumatic system for receiving carriers which enter through an inlet 22 and to direct the carriers out through either the main outlet 24 or one of two branch outlets 26, 28. In order to achieve this carrier movement, air is drawn in through the inlet 22 and out the main outlet 24. When the selector directs a carrier through one of the branch outlets 26, 28 air passes from the inlet 22 and down the corresponding branch outlet before being recovered through secondary inlets 30, 32 from whence the air passes down the main outlet 24. A suitable air circuit for this purpose will be described with reference to FIG. 7.

In the position shown, inlet 22 is connected directly to outlet 24. A flexible coupling 34 is attached to the inlet 22 and connected to an end of a movable tube 36 which in turn is connected to a seal assembly 38 attached to outlet 24. The inlets and outlets are preferably welded to an air-tight main housing 40.

Line selection is achieved by transferring the seal assembly 38 from one outlet to another as will be described. Any mis-alignment of the movable tube 36 and inlet 22 is accommodated by the flexible coupling 34 which will be described with reference to FIGS. 3 and 4.

The main housing 40 consists of an end wall 42 to which inlet 22 is welded, a further end wall 44 to which the outlets 24, 26 and 28 are welded, side walls 46 and 48 which diverge from end wall 42 and terminate at end wall 44, top wall 50, and bottom wall 52. The top and bottom walls 50, 52 are arranged in generally parallel relationship and a cover 54 is positioned on the top wall 50 to contain parts of the switching mechanism (which will be described with reference to FIGS. 5 and 6) and associated electrical apparatus. As seen in FIG. 2, the line selector is normally activated from a control circuit of a type commonly used with this type of device. A pair of openings 56, 58 are provided in the top wall 50 to provide access for parts of the switching mechanism as will be described.

Reference is next made to FIG. 3 which illustrates parts of the flexible coupling 34. Inlet 22 guides carriers downstream into the main housing 40 and terminates in an end portion 60. This portion carries a ring 62 welded externally about the portion and the portion 60 defines a pair of diametrically opposed axial slots 64, 66. At the other end of the flexible coupling 34, the movable tube 36 terminates in an end portion 68 similar to end portion 60. The portion 68 defines a further pair of slots 70 (one of which can be seen in this view) and carries a ring 71. On assembly, the portions 60, 68 are placed substantially in alignment with a tubular coupling piece 72 having the same internal and external diameters as the movable tube 36 and the inlet 22.

Coupling piece 72 carries a pair of rings 74, 76 (similar to rings 62 and 71) which are welded in place. The end of the piece 72 nearer to the tube end portion 68 is typical of both ends and this end is cut back axially to define angled faces 77 which meet at diametrically opposed points. This end of the piece 72 also defines a pair of axial slots 78, 80 disposed about a diameter at right angles to a diameter from which the cut back begins. Similar slots 82 (one of which is shown) are formed in the opposite end of the coupling piece 72 and this end is also cut back to define angled faces 83.

The coupling piece 72 is held in alignment with the inlet 22 by a first rolled spring 84 which has a generally tubular cross-section adapted to engage about the end 3 portion 60and about an adjacent portion of the cons pling piece 72. The spring 84 is located against rotation on the end portion 60 and piece 72 by recesses 86, and

88 (one of which is shown in this view) which engage about respective short pins 90, 92 welded to the coupling piece 72 and to the end portion 60. Axial location is provided by the rings 62,76. Although being generally tubular, the spring is discontinuous at an axial gap 94 which permits the spring to deform radially as will be described. A pair of shoes 96, 98 are riveted to the inner surfaces of the spring in. alignment with respec tive pairs of recesses 86, 88. These shoes'96, 98fit within the slots 64, 66 and 82 and the thickness of the shoes is'similar to that of the walls of the end portion 60 and the coupling piece 72.

A second rolled spring 84 is provided and this spring is similar to the spring 84. Parts of spring 84 similar to those already described with reference to spring 84 are given primed numerals inthe drawings.

Reference is now made to FIG. 4 which is a top view of the flexible coupling 34, movable tube 36 and seal assembly 38. The flexible coupling is shown in the position it occupies when the seal assembly 38 is in position against a branch outlet 26. In this position, the rolled spring 84 has been deformedradially as the coupling tive to the outlet 26. A further function of these sur- I an equalforce on the flexible coupling 34 to prevent separation of parts of the coupling. Both the spring 112 and the collar 114 fit snugly on the outersurface of'the tube 36 so that the tube guides both the spring and the collar 114 to move axially. The downstream-end of the collar 114 defines a radial flange 116 having part of its outer surface conical in shape. A complementary flange 118 is formed on the outlet-26 and similar complementary flanges arealso formed on the other outlets.

O-ring 120'is located. In the position shown in FIG. 4, the Oring 120 is compressed against the face of flange 118 by the spring 112.

l The complementary conical portions of the flanges 116, 118 act to locate the seal assembly-positively relafaces is to limit possible damage to the O-ring 120 when the seal assembly is moved from one outlet to another.

through the inlet, the shoe 96 guides the carrier into the coupling portion. This situation isof course reversed when the seal assembly 38 is in position against the.

other branch outlet 28 when the shoe 96 guides the carrier into the coupling piece'72.

The rolled spring 84 functions in a similar manner to the spring 84 to guide the carrier from the coupling piece 72 to the movable tube 36. As a result, the angle between the inlet 22 and the movable tube36 is equal to twice the total angle which the coupling piece may be moved through relative to the inlet 22 because of the similarity between the ends of the coupling piece 72.

The flexible coupling '34 is pneumatically'sealed by a protective sleeve 100 held in place at its ends on the As soon asthe seal assembly is moved out of alignment with the" outlet 26, the conical surface of flange 116 rides on the complementary surface of flange 118, and

the collar 114 is displaced axially upstream'away from the outlets to permit the conical portion of flange 116 to ride. over the flange 118. As soon, as the seal assem' bly 38 is in alignment with another outlet, the collar 114 moves axially downstream bringing the conical surface of flange 116 into locating engagement with the complementary surface of a further flange 118 on another outlet. 7

The seal assembly 38 is sealed pneumatically by a flexible sleeve 122 which extends from the collar 114 to the movable tube 36. The sleeve 122 is held in place by two hose clamps 124, 126 located respectively about the collar 114 and tube 36. p

Reference is next made to FIG. 5 to further described the structure of the main housing 40 and also to describe apair of switching mechanisms 128, 128 prov vided for moving the seal assembly between outlets as willbe described withreference to this figure and to FIG; 6.

As seen in FIG. 5, the side walls 46, 48 are flanged inwardly at their upper extremities to receive, screws I 130 which pass through top wall50 and through a gasket 132 to seal the top 50 to the side walls 46, 48. A

similar arrangement is provided at the end walls 42, 4,4

inlet 22 and movable tube 36 by respective hose clamps 102, 104. The rings 62, 74, 76 and 71 are proportioned to support the sleeve to avoid possible damage to the sleeve caused by engagement with the ends of V springs 84, 84' and associated parts. Sleeve 100 ensures that no air is drawn through the flexible coupling 34 and into the movable tube 36. V V

As seen in FIG. 4, the movable tube 36 is connected at its downstream end to the seal assembly 38'. Also, and as will be described with reference to FIG. 6, the tube 36 is coupled to a follower plate 106 forming part of a switch mechanism for transferring the seal assembly from one outlet to another.

The seal assembly 38 consists of a ring 108 attached to the movable tube 36 by a grub screw 110 for locating a coiled compression spring 11 2. This spring biases a collar 114 downstream towardsthe outlets and applies (FIG. 1) so that the gasket 132 is continuous and 1' screws are provided at intervals to provide an air-tight seal. 7

As described with reference to FIG. 1,the top wall 1 50 describes a pair of openings 56, 58 which, as seen i in FIG. 5, are covered by respective support plates 134, 134. These plates'are held in place by respective screws 136, 136' and "gaskets 138,138 are provided for sealing. the support plates to the: top wall 50 of the main housing 40.

The switching mechanism 128 will now be described.

Because this mechanism is similar to the mechanism 128' only the mechanism 128 will be described in detail. Parts of mechanism [28"correspondirig to those parts to be described will be given primed numerals to simplify reference in further description.

Mechanism 128 includes an electric motor 140 coupled electrically to the control circuit shown in FIG. 2. The motor 140 is connected mechanically through a reduction gear box 142 to an output shaft 144 on which a cam 146 ismounted below the support plate 134. The

The flange 116 defines an annular recessin which an V output shaft 144 passes through a bush 148 which limits air seepage past the support plate 134 and also acts as a bearing for the output shaft 144. Motor 140 and associated gear box 142 are mounted as a unit on the support plate 134 by suitable screws 150 which pass through the support plate 134 and are threadably engaged in the housing of the gearbox I42.

Cam 146 is locked to the output shaft 144 by a pair of grub screws 152 threaded into the cam 146 at right angles to one another. At the other end of the cam, a pin 154 extends downwardly and has a cam roller 156 rotatably mounted on it. The roller 156 is held on the pin 154 by a conventional circlip engaged in a groove in the pin 154. The upper surface of the cam 146 adjacent pin l54 is chamfered transversely to both sides to define a pair of ramps 158 for engaging conventional ball-ended limit switches 160, 162 mounted conventionally in the support plate 134.

Reference is next made to FIG. 6 to describe parts of the mechanisms 128, 128' associated directly with the movable tube 36. As previously described, a follower plate 106 is coupled to the tube 36. The plate 106 is attached to saddle plates 164, each of which is welded to the tube 36 and proportioned so that the plate 106 is spaced from the tube 36. A cam lock 166 is attached centrally to the underside of the follower plate 106 and consists of a leaf spring 168 having turned up ends and shaped such that the ends are normally displaced from the plate 106 towardsthe tube 36. A pair of stop members 170, 170' are provided such that upon deflecting the leaf spring 168 upwardly at either end, the stop member at that end will become engaged in a corresponding one of a pair of months 172, 172'. These mouths normally provide access for respective cam rollers 156, 156' into axial slots 174, 174'. However, when a stop member moves into a mouth, the corresponding roller 156, 156 is trapped in a respective one of the slots 174, 174',

A further pair of saddle plates 176 are welded to the underside of the tube 36 and these plates support small wheels 178 adapted to roll on the bottom wall 52 (FIG. 5) of the main housing 40. A similar pair of wheels 180 are provided on the follower plate 106 for rolling engagement with the underside of top wall 50. The wheels 178, 180 serve to locate the movable tube 36 vertically thereby ensuring that the seal assembly 38 (FIG. 1) always seats on a selected one of the outlets 24, 26 or 28. Also where a vacuum system is used, the walls 50, 52 tend to move toward one another. However, because there are wheels riding in both walls the axis of the movable tube 36 remains in position for alignment with the outlets.

In use, the movable tube 36 and seal assembly 38 will, for most of the time, be aligned with the main outlet 24 as shown in FIG. I. In this position, the mechanisms 128, 128 will be in the relative positions shown in FIGS. 5 and 6. The cam rollers 156, 156 will be located in respective slots 174, 174' adjacent mouths 172, 172'. Assume now that the control circuit (FIG. 2) actuates the motor 140 resulting in the cam 146 rotating with the shaft 144. As the cam 146 turns the cam roller 156 moves along the slot 174 and draws the follower plate 106 together with tube 36 and seal assembly 38 transversely towards branch outlet 28 (FIG. I). As previously described, initially the movement results in collar 114 (FIG. 4) of the seal assembly moving axially away from the outlet thereby lifting the O-ring 120 out of contact with flange 118 of the associated outlet. As the cam 146 continues to turn, the mouth 172 in plate 106 passes the cam roller 156 so that the roller 156' is no longer within the confines of the follower plate 106.

Cam roller 156 is in contact with the outer surface of slot 174 while moving the follower plate towards the side wall 48. When the cam has passed through the roller 156 begins to return towards mouth 172. Consequently, there is a possibility that the roller 156 could move out of the mouth 172 before the seal assembly 38 has seated properly on the branch outlet 28 (FIG. 1). To avoid this possibility, the cam lock 166 is used to cooperate with a bracket 182 attached to side wall 48 by fasteners 184. The bracket 182 includes a ramp portion 186 for combining with a curved outer end of the leaf spring 168 so that as the follower plate 106 approaches wall 48, the leaf spring is deflected upwardly and the stop member is moved into position within the mouth 172. Because member 170 is proportioned and positioned so that it effectively forms a continuation of the outer surface of slot 174, the cam roller 156 can bear against the member 170 before coming to rest adjacent this member. The seal assembly 38 is then located against the branch outlet 28 as previously described with reference to FIG. 4.

The control circuit (FIG. 2) is coupled to the limit switches 160, 162 to sense the position of cam 146 and hence of the seal assembly 38. Consequently with the seal assembly aligned with outlet 28 (FIG. 1) the limit switch 162 is engaged by the cam 146. When the main outlet 24 is to be re-connected to the inlet 22, the cam 146 repeats the movement and the cam roller 156 bears against the inner surface 174 to return the follower plate to the original position. When the cam 146 returns to the position shown in FIG. 5, the cam engages switch 160 so that the control circuit is again aware of the position of the seal assembly.

In switching from the main outlet 24 to the branch outlet 26, the motor 140' is activated and the cam 146 operates with the cam roller 156' in the slot 174. In this instance, cam roller 156 is released through mouth 172 so that it does not interfere with the movement of the line selector in coupling the branch outlet 26 to the inlet 22 (FIG. 1).

Reference is now made to FIG. 7 which illustrates a simple pneumatic system incorporating a line selector 188 similar to that described previously. The system also includes another line selector 190 and a main line 192 passes from a sending station 194, through the selectors 190,188 before ending at a receiving station 196. Air is drawn from the sending station 194 to a point adjacent the receiving station 196 by a vacuum pump 198 for moving conventional carriers through the system. A check valve 199 prevents air entering the system through station 196 but permits carriers to pass on their way to the station 196.

As previously described, the line selectors can be switched to deliver the carrier either to the main line 192 or to branch lines. Line selector 190 can deliver carriers either to receiving station 200 by way of branch line 202 or to station 204 by way of branch line 206. Similarly, line selector 188 serves stations 208, 210 by way of respective branch lines 212, 214.

The stations 200, 208 are fed by downwardly inclined branch lines 202, 212 so that once the carrier leaves a I respective one of selectors 188, 190 and enters a correis feeding line 212, air must continue to leave the. selector through the main line 192. This is achieved in one of many ways. For instance (and aswill be described in more detail) the portion of the. outlet'inside the main housing of the line selector can be perforated to permit air drawn into the line selector to find its way out through the main line 192. A check valve 216 prevents air from being drawn into the system from station 208 l but permits carriers to pass on their way to the station.

A similar arrangement is used for line selector 190.

When line selector 188 is switched to feed branch line 214, carriers are fed by air moving into the line 214 and the air then passes through a secondary line 2118 back through the line selector and out by way of the main line 192 on its way to pump 198. Check valve 220 prevents air entering the system through station 210.

A further secondary line 222 is used in connection with branch line 206. In this case the secondary line 222 joins main line 192 to feed air back after the air has passed part of the way down branch line 206'. The line 206is therefore an alternative for the line218..

Reference is now made to FIG. 8 to more fully d escribe the passage of air through selectors 190 and 188 (FIG. 7) when feeding respective branch lines 202, 212. As seen in FIG. 8 (which can be compared with a corresponding part of FIG. 1) an outlet 224 is provided having perforations 226 so that the air path is from a seal assembly 228, through the perforation 226 and then through a main outlet 230.0f course it will be evident that a secondary line arrangement (such as lines 218 or 222 FIG. 7) can be used in place of the perforations.

The perforations can also be used for a different purpose with some modifications to the sizes of the perforations. For instance, the branch line 214 seen in FIG. 7 may be required to slow down the speed of the carrier passing from the main line. This can be done by arranging the perforations to bleed off some of the air passing towards line 214 thereby reducing the force available for driving the carrier.

In order to increase the range of uses of a given line selector, perforations 226 can be provided at each branch outlet 26, 28 (FIG. I) and a rotatable cover 232 placed over the. perforations as shown in ghost outline in FIG. 8. In the position shown in FIG. 8, openings in the cover would be aligned with the perforations 226. By rotating the cover the perforations could be closed or opened partially as desired for a given branch line.

The line selector 10 has been described in a horizontal position. However, it will be appreciated that all of the movements of the parts of the selector are 'controlled positively. As a result the selector can be used in any position dependent upon the requirements of a particular installation The selector and associated exemplary system have been described in use with a vacuum system and with the carriers entering a single inlet for selective direction through one of three outlets. It will be evident to those skilled in the art that a two outlet selector can be used and that a pressurized system can be used with suitable stations. Further, so that the selector then has three inlets receiving carriers, and one outlet.

7 It willnow be evident from the foregoing description that the line selector, herein described can be used in many different situations occurring in pneumatic systerns and that the foregoing description is exemplary of some of these situations.

lc'laim: V

l. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising:

a main housing; a

an inlet through which the carrier enters the main housing;

a main outlet and a branch outlet through which the carrier selectively leaves the line selector;

a flexible coupling located withinthe housing and atcoupling comprising a tubular coupling piece having an angled face at one end thereof; the inlet defining an end face adjacent said angled face and the angled face being removed from said end face when the seal assembly is in engagement with the main outlet and substantially in engagement with saidend face when the seal assemblyis in engagement with the branch outlets; a rolled spring in snug engagement with the outer surfaces of the coupling piece and'the inlet for biasing the coupling piece into axial alignment with the inlet, the

the carrier does; not snag on the angled face of the I coupling piece;

a seal assembly coupled to the other end of the flexi- I ble coupling for receiving the carrier afterthe car- I rier leaves the flexible coupling; the sealassembly and outlets defining means for loeating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet; and a a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engage-- ment with another of the outlets.

2. A line selector as claimed in claim 1 in which the other end of the coupling piece defines a further angled face positioned relative to the axis of the coupling piece.

similarly to the position of the firstmentioned angled face, and in which the line selector further comprises 7 a movable tube: connected at one end thereof to the rated when the seal assembly is in engagement with the main outlet and substantially in engagement with said movable tube end face when the seal assembly is in enthe selector can be reversed tached at a first end thereof to the inletthe flexible.

gagement with the branch outlet, and in which the line selector further comprises:

a second rolled spring in snug engagement with the outer surfaces of the coupling piece and the movable tube for biasing the coupling piece and movable tube into axial alignment one with the other, the spring being resiliently deformed when the seal assembly is in engagement with the branch outlet;

a second shoe attached to an inner surface of the second rolled spring;

the movable tube and the coupling piece defining a second pair of adjacent and aligned axial slots, one of the slots being in the coupling piece and located at a part of the further angled face most remote from the movable tube when the seal assembly is in engagement with the main outlet; and

said second shoe being located in said second pair of slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the movable tube end face.

3. A flexible coupling for use in pneumatic tube systems of the type used to transport carriers from station to station, the flexible coupling comprising:

a tubular coupling piece having an angled face at one end thereof;

an inlet defining an end face adjacent said angled face, and the angled face being removed from said end face when the coupling piece is in alignment with the inlet and substantially in engagement with said end face when the coupling piece is in a position of maximum angular displacement from the axis of the inlet;

a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the coupling piece is displaced angularly from the axis of the inlet;

a shoe attached to an inner surface of the spring;

the inlet and the coupling piece defining a pair of adjacent and aligned axial slots with the slot in the coupling piece being located at a part of the angled face most remote from the inlet end face when the coupling piece is in alignment with the inlet; and

said shoe being located in said slot to guide a carrier passing through the flexible coupling so that the carrier does not snag on the angled face of the coupling piece.

4. A flexible coupling for use in pneumatic tube systems of the type used to transport carriers from station to station, the flexible coupling comprising:

a tubular coupling piece having a pair of angled faces at one end thereof, the angled faces extending one to each side of a diameter of the tubular coupling piece;

an inlet defining an end face adjacent said angled faces, and the angled faces being removed from said end face when the coupling piece is in alignment with the inlet and respectively substantially in engagement with said end face when the coupling piece is in a respective one of two positions of maximum angular displacement from the axis of the inlet;

a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the coupling piece is displaced angularly from the axis of the inlet;

a pair of shoes attached to diametrically opposed portions of an inner surface of the spring;

the inlet and the coupling piece defining two pairs of adjacent and aligned axial slots with the slots in the coupling piece being located one at each of the parts of the angled faces most remote from the inlet end face when the coupling piece is aligned with the inlet; and

said shoes being located in said slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the angled faces of the coupling piece.

5. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station the line selector comprising:

a main housing;

an inlet through which the carrier enters the main housing;

a main outlet and first and second branch outlets through which the carrier selectively leaves the line a selector;

a flexible coupling located within the housing and attached at a first end thereof to the inlet;

a movable tube coupled at a first end thereof to the flexible coupling;

a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube;

the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet;

a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets;

the flexible coupling comprising:

a tubular coupling piece having a pair of angled faces at one end thereof, the angled faces extending one to each side of a diameter of the tubular coupling piece, the inlet defining an end face adjacent said angled faces, and the angled faces being removed from said end face when the seal assembly is in engagement with the main outlet and respectively substantially in engagement with said end face when the seal assembly is in engagement with respective branch outlets; a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the seal assembly is in engagement with either one of said branch outlets; a pair of shoes attached to diametrically opposed portions of an inner surface of the spring; the inlet and the coupling piece defining two pairs of adjacent and aligned axial slots with the slots in the coupling piece being located one at each of the parts of the angled faces most remote from the inlet end face when the seal assembly is in engagement with the main outlet; and said shoes being located in said slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the angled faces of the coupling piece. 7

6. A line selector as claimed in claim 5 in which the other end of the coupling piece defines a further pair of angled faces extending to either side of a further diameter of the coupling piece, said first-mentioned diameter and said further diameter being substantially parallel, the line selector further comprising a movable tube connected at one end thereof to the seal assembly and the other end thereof defining an end face adjacent said further, angled faces, the movable tube end face and said further angled faces being separated when the seal assembly is in engagement with the main outlet and respectively substantially in engagement with said mov-.

assembly is in engagement with either one of said branch outlets; a second pair of shoes attached at diametrically opposed positions on an inner surface of the second rolled spring;

the movable tube and the coupling piece defining two second pairs of adjacent and aligned axial slots with the slots in the coupling piece being located. at parts of the furtherangled faces most remote from the movable tube when the seal assembly is in engagement with the main outlet; and

said second shoes being located in said pairs of second slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the movable tube end face.

7. A line selector as claimed in clair'n 5 in which the locating means comprises: a collar mounted on the movable tube for axial movement thereon; means resiliently biasing the collar axially towards the outlets; and the collar and each of theoutlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet.

8. A line selector as claimed in claim 7 in which at least one of the branch outlets is perforated within the housing to permit at least a portion of air passing through the seal assembly to bleed from the perforated branch outlet to the mainoutlet.

9. A line selector as claimed in claim 5 in which the switching mechanism is one of a pair of switching mechanisms each of which is operable tomove the seal assembly between the main outlet and a respective one of the branch outlets, the switching mechanisms including a follower plate coupled to the seal assembly and each of the switching mechanisms comprising: a cam for engagement with the follower plate; and drive means operable to rotate the cam for moving the follower plate whereby the seal assembly is moved between engagement with the main outletand engagement with a respective one of the branch outlets.

10. A line selector as claimed in claim. 9 in which at least one of the branch outlets is perforated within the housing to permit at least a fraction of air passing through the seal assembly to bleed from the perforated branch outletto the main outlet. a

i 11. A line selectorfor use in pneumatic tube systems of the type used. to transport carriers fromstation to station, the line selector comprising;

a main housing;

an inlet through which the carrier enters the main housing;

a main outlet and a branch outletthrough which the carrier selectively leaves theflinewselector;

a flexiblecoupling located'within the housing and attached at a first end thereof to the inlet;

a movable tube coupled at a first end thereof to the flexible coupling;

a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube;

the seal assembly and outlets defining means; for loeating the seal assembly selectively againsteach one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a col lar mounted on the movable tube for axial movement thereon; means coupled to the movable tube the branch outlet being perforated within the housing to permit at least a portion of air passing through A the seal assembly to bleed from the branch outlet to the main outlet.

12. A line selector as claimed in claim 11 and further comprising a covercoupled to the branch outlet and adapted for movement relative to the branch outlet to 0 selectively close at least portions of the perforations.

13. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to a a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube;

the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexi-t ble coupling the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet;

a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets; and

at least one of the branch outlets being perforated within the housing to permit at least a fraction of air passing through the seal assembly to bleed from the perforated branch outlet to the main outlet.

14. A line selector as claimed in claim 13 and further comprising a cover coupled to the branch outlet and adapted for movement relative to the branch outlet to selectively close at least portions of the perforations.

15. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising:

a main housing;

an inlet through which the carrier enters the main housing;

a main outlet and a branch outlet through which the carrier selectively leaves the line selector;

a flexible coupling located within the housing and attached at a first end thereof to the inlet;

a movable tube coupled at a first end thereof to the flexible coupling;

a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube;

the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to 'prevent separation of the flexi ble coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; and

a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets, the switching mechanism comprising:

a follower plate attached to the movable tube and having a slot extending axially; a cam for engagement with the follower plate, the cam having a roller located in the slot so that as the cam rotates the roller moves in the slot and imparts movement to the follower plate and hence to the movable tube and seal assembly; and

drive means operable to rotate the cam for moving the follower plate whereby the seal assembly is moved out of engagement with one of said outlets and into engagement with another of the outlets.

16. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising:

a main housing;

an inlet through which the carrier enters the main housing;

a main outlet and first and second branch outlets through which the carrier selectively leaves the line selector;

a flexible coupling located within the housing and attached at a first end thereof to the inlet;

a movabale tube coupled at a first end thereof to the flexible coupling;

a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube;

the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon, means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; and

a pair of switching mechanisms coupled to the main housing each of the switching mechanisms being operable to move the seal assembly between the main outlet and a respective one of the branch outlets, the switching mechanisms including a follower plate coupled to the seal assembly and each of the switching mechanisms comprising: a cam for engagement with the follower plate; and drive means operable to rotate the cam for moving the follower plate whereby the seal assembly is moved between engagement with the main outlet and engagement with a respective one of the branch outlets.

17. A line selector as claimed in claim 16 in which the follower plate defines a pair of axial slots and in which each of the cams includes a roller engaged in a respective one of the slots when the seal assembly is in engagement with the main outlet, the follower plate further defining a pair of mouths extending transversely from the respective slots to the sides of the follower plate to provide access for the cam rollers into the slots so that upon operation of one of the drive mechanisms to rotate a corresponding one of the cams, the associ-1 ated cam roller rides in the corresponding slot and thereby moves the seal assembly out of engagement with the main outlet and into engagement with a corresponding branch outlet, the initial movement of the follower plate moving the respective mouth past the other of the rollers to free said other roller from the follower plate, said switching mechanisms further comprising a cam lock operable to close the respective mouths as the l seal assembly approaches a corresponding one of the branch outlets whereby the roller associated with the cam which is moving the seal assembly towards the branchoutlet is trapped in the corresponding slot.

18. A line selector as claimed'in claim 17 and'further a corresponding one of the outlets. 

1. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising: a main housing; an inlet through which the carrier enters the main housing; a main outlet and a branch outlet through which the carrier selectively leaves the line selector; a flexible coupling located within the housing and attached at a first end thereof to the inlet the flexible coupling comprising a tubular coupling piece having an angled face at one end thereof; the inlet defining an end face adjacent said angled face and the angled face being removed from said end face when the seal assembly is in engagement with the main outlet and substantially in engagement with said end face when the seal assembly is in engagement with the branch outlets; a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the seal assembly is in engagement with said branch outlet; a shoe attached to an inner surface of the spring; the inlet and the coupling piece defining a pair of adjacent and aligned axial slots with the slot in the coupling piece being located at a part of the angled face most remote from the inlet end face when the seal assembly is in engagement with the main outlet; and said shoe located in said slots to guide a carRier passing through the flexible coupling so that the carrier does not snag on the angled face of the coupling piece; a seal assembly coupled to the other end of the flexible coupling for receiving the carrier after the carrier leaves the flexible coupling; the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet; and a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets.
 2. A line selector as claimed in claim 1 in which the other end of the coupling piece defines a further angled face positioned relative to the axis of the coupling piece similarly to the position of the firstmentioned angled face, and in which the line selector further comprises a movable tube connected at one end thereof to the seal assembly and the other end thereof defining an end face adjacent said further angled face, the movable tube end face and said further angled face being separated when the seal assembly is in engagement with the main outlet and substantially in engagement with said movable tube end face when the seal assembly is in engagement with the branch outlet, and in which the line selector further comprises: a second rolled spring in snug engagement with the outer surfaces of the coupling piece and the movable tube for biasing the coupling piece and movable tube into axial alignment one with the other, the spring being resiliently deformed when the seal assembly is in engagement with the branch outlet; a second shoe attached to an inner surface of the second rolled spring; the movable tube and the coupling piece defining a second pair of adjacent and aligned axial slots, one of the slots being in the coupling piece and located at a part of the further angled face most remote from the movable tube when the seal assembly is in engagement with the main outlet; and said second shoe being located in said second pair of slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the movable tube end face.
 3. A flexible coupling for use in pneumatic tube systems of the type used to transport carriers from station to station, the flexible coupling comprising: a tubular coupling piece having an angled face at one end thereof; an inlet defining an end face adjacent said angled face, and the angled face being removed from said end face when the coupling piece is in alignment with the inlet and substantially in engagement with said end face when the coupling piece is in a position of maximum angular displacement from the axis of the inlet; a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the coupling piece is displaced angularly from the axis of the inlet; a shoe attached to an inner surface of the spring; the inlet and the coupling piece defining a pair of adjacent and aligned axial slots with the slot in the coupling piece being located at a part of the angled face most remote from the inlet end face when the coupling piece is in alignment with the inlet; and said shoe being located in said slot to guide a carrier passing through the flexible coupling so that the carrier does not snag on the angled face of the coupling piece.
 4. A flexible coupling for use in pneumatic tube systems of the type used to transport carriers from station to station, the flexible coupling comprising: a tubular coupling piece having a pair of angled faces at one end thereof, the angled faces extending one to each side of a diameter of the tubular coupling piece; an inlet defining an end face adjacent said angled faces, and the angled faces being removed from said end Face when the coupling piece is in alignment with the inlet and respectively substantially in engagement with said end face when the coupling piece is in a respective one of two positions of maximum angular displacement from the axis of the inlet; a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the coupling piece is displaced angularly from the axis of the inlet; a pair of shoes attached to diametrically opposed portions of an inner surface of the spring; the inlet and the coupling piece defining two pairs of adjacent and aligned axial slots with the slots in the coupling piece being located one at each of the parts of the angled faces most remote from the inlet end face when the coupling piece is aligned with the inlet; and said shoes being located in said slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the angled faces of the coupling piece.
 5. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station the line selector comprising: a main housing; an inlet through which the carrier enters the main housing; a main outlet and first and second branch outlets through which the carrier selectively leaves the line selector; a flexible coupling located within the housing and attached at a first end thereof to the inlet; a movable tube coupled at a first end thereof to the flexible coupling; a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube; the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets; the flexible coupling comprising: a tubular coupling piece having a pair of angled faces at one end thereof, the angled faces extending one to each side of a diameter of the tubular coupling piece, the inlet defining an end face adjacent said angled faces, and the angled faces being removed from said end face when the seal assembly is in engagement with the main outlet and respectively substantially in engagement with said end face when the seal assembly is in engagement with respective branch outlets; a rolled spring in snug engagement with the outer surfaces of the coupling piece and the inlet for biasing the coupling piece into axial alignment with the inlet, the spring being resiliently deformed when the seal assembly is in engagement with either one of said branch outlets; a pair of shoes attached to diametrically opposed portions of an inner surface of the spring; the inlet and the coupling piece defining two pairs of adjacent and aligned axial slots with the slots in the coupling piece being located one at each of the parts of the angled faces most remote from the inlet end face when the seal assembly is in engagement with the main outlet; and said shoes being located in said slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the angled faces of the coupling piece.
 6. A line selector as claimEd in claim 5 in which the other end of the coupling piece defines a further pair of angled faces extending to either side of a further diameter of the coupling piece, said first-mentioned diameter and said further diameter being substantially parallel, the line selector further comprising a movable tube connected at one end thereof to the seal assembly and the other end thereof defining an end face adjacent said further angled faces, the movable tube end face and said further angled faces being separated when the seal assembly is in engagement with the main outlet and respectively substantially in engagement with said movable tube end face when the seal assembly is in engagement with the respective branch outlets, and in which the line selector further comprises: a second rolled spring in snug engagement with the outer surfaces of the coupling piece and the movable tube for biasing the coupling piece and movable tube into axial alignment one with the other, the spring being resiliently deformed when the seal assembly is in engagement with either one of said branch outlets; a second pair of shoes attached at diametrically opposed positions on an inner surface of the second rolled spring; the movable tube and the coupling piece defining two second pairs of adjacent and aligned axial slots with the slots in the coupling piece being located at parts of the further angled faces most remote from the movable tube when the seal assembly is in engagement with the main outlet; and said second shoes being located in said pairs of second slots to guide a carrier passing through the flexible coupling so that the carrier does not snag on the movable tube end face.
 7. A line selector as claimed in claim 5 in which the locating means comprises: a collar mounted on the movable tube for axial movement thereon; means resiliently biasing the collar axially towards the outlets; and the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet.
 8. A line selector as claimed in claim 7 in which at least one of the branch outlets is perforated within the housing to permit at least a portion of air passing through the seal assembly to bleed from the perforated branch outlet to the main outlet.
 9. A line selector as claimed in claim 5 in which the switching mechanism is one of a pair of switching mechanisms each of which is operable to move the seal assembly between the main outlet and a respective one of the branch outlets, the switching mechanisms including a follower plate coupled to the seal assembly and each of the switching mechanisms comprising: a cam for engagement with the follower plate; and drive means operable to rotate the cam for moving the follower plate whereby the seal assembly is moved between engagement with the main outlet and engagement with a respective one of the branch outlets.
 10. A line selector as claimed in claim 9 in which at least one of the branch outlets is perforated within the housing to permit at least a fraction of air passing through the seal assembly to bleed from the perforated branch outlet to the main outlet.
 11. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising: a main housing; an inlet through which the carrier enters the main housing; a main outlet and a branch outlet through which the carrier selectively leaves the line selector; a flexible coupling located within the housing and attached at a first end thereof to the inlet; a movable tube coupled at a first end thereof to the flexible coupling; a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube; the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and furtHer including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets; and the branch outlet being perforated within the housing to permit at least a portion of air passing through the seal assembly to bleed from the branch outlet to the main outlet.
 12. A line selector as claimed in claim 11 and further comprising a cover coupled to the branch outlet and adapted for movement relative to the branch outlet to selectively close at least portions of the perforations.
 13. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising: a main housing; an inlet through which the carrier enters the main housing; a main outlet and first and second branch outlets through which the carrier selectively leaves the line selector; a flexible coupling located within the housing and attached at a first end thereof to the inlet; a movable tube coupled at a first end thereof to the flexible coupling; a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube; the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets; and at least one of the branch outlets being perforated within the housing to permit at least a fraction of air passing through the seal assembly to bleed from the perforated branch outlet to the main outlet.
 14. A line selector as claimed in claim 13 and further comprising a cover coupled to the branch outlet and adapted for movement relative to the branch outlet to selectively close at least portions of the perforations.
 15. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising: a main housing; an inlet through which the carrier enters the main housing; a main outlet and a branch outlet through which the carrier selectively leaves the line selector; a flexible coupling located within the housing and attached at a first end thereof to the inlet; a movable tube coupled at a first end thereof to the flexible coupling; a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube; the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seAl assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon; means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; and a switching mechanism coupled to the main housing and operable to move the seal assembly out of engagement with one of the outlets and into engagement with another of the outlets, the switching mechanism comprising: a follower plate attached to the movable tube and having a slot extending axially; a cam for engagement with the follower plate, the cam having a roller located in the slot so that as the cam rotates the roller moves in the slot and imparts movement to the follower plate and hence to the movable tube and seal assembly; and drive means operable to rotate the cam for moving the follower plate whereby the seal assembly is moved out of engagement with one of said outlets and into engagement with another of the outlets.
 16. A line selector for use in pneumatic tube systems of the type used to transport carriers from station to station, the line selector comprising: a main housing; an inlet through which the carrier enters the main housing; a main outlet and first and second branch outlets through which the carrier selectively leaves the line selector; a flexible coupling located within the housing and attached at a first end thereof to the inlet; a movabale tube coupled at a first end thereof to the flexible coupling; a seal assembly coupled to the other end of the movable tube for receiving the carrier after the carrier passes through the flexible coupling and the movable tube; the seal assembly and outlets defining means for locating the seal assembly selectively against each one of the outlets and further including means for pneumatically sealing the seal assembly to the selected outlet, the locating means comprising: a collar mounted on the movable tube for axial movement thereon, means coupled to the movable tube for resiliently biasing the collar axially towards the outlets and the tube into firm engagement with the flexible coupling to prevent separation of the flexible coupling; the collar and each of the outlets defining complementary conical surfaces for engagement one with the other to locate the seal assembly relative to said selected outlet; and a pair of switching mechanisms coupled to the main housing each of the switching mechanisms being operable to move the seal assembly between the main outlet and a respective one of the branch outlets, the switching mechanisms including a follower plate coupled to the seal assembly and each of the switching mechanisms comprising: a cam for engagement with the follower plate; and drive means operable to rotate the cam for moving the follower plate whereby the seal assembly is moved between engagement with the main outlet and engagement with a respective one of the branch outlets.
 17. A line selector as claimed in claim 16 in which the follower plate defines a pair of axial slots and in which each of the cams includes a roller engaged in a respective one of the slots when the seal assembly is in engagement with the main outlet, the follower plate further defining a pair of mouths extending transversely from the respective slots to the sides of the follower plate to provide access for the cam rollers into the slots so that upon operation of one of the drive mechanisms to rotate a corresponding one of the cams, the associated cam roller rides in the corresponding slot and thereby moves the seal assembly out of engagement with the main outlet and into engagement with a corresponding branch outlet, the initial movement of the follower plate moving the respective moUth past the other of the rollers to free said other roller from the follower plate, said switching mechanisms further comprising a cam lock operable to close the respective mouths as the seal assembly approaches a corresponding one of the branch outlets whereby the roller associated with the cam which is moving the seal assembly towards the branch outlet is trapped in the corresponding slot.
 18. A line selector as claimed in claim 17 and further comprising means responsive to the positions of said cams to de-energize the respective switching mechanisms as the seal assembly moves into engagement with a corresponding one of the outlets. 